NotoriousARG

I am running a 2006 Octavia VRS and recently I've noticed the engine fan is really noisy. On closer inspection even when the air conditioning is running only the larger of the two fans will spin. The smaller fan wont start at all. I've had my mate plug a diagnostic computer into the car and it's not showing any errors. I've also replaced the fan fuse just in case but it's still doing the same. Do I need a whole new fan set?